1. Field of the Invention
The present invention relates to a high-frequency module that sends and receives a plurality of types of high-frequency signals in a switchable manner.
2. Description of the Related Art
Hitherto, various types of high-frequency modules have been devised, each of which includes a plurality of SAW filters and can send and receive a plurality of communication signals in different frequency bands by using just one antenna. In that type of high-frequency module, unless a circuit for transmitting a communication signal in another different frequency band is designed to provide a phase of about 180° for the communication signal in the frequency band to be sent and received, a transmission loss of the communication signal in the frequency band to be sent and received is increased in the use of the high-frequency module. As one example of a method for solving the above-described problem, in a high-frequency module disclosed in Japanese Unexamined Patent Application Publication No. 2003-87076, a phase adjustment circuit is provided for phase adjustment in a line connecting the SAW filter and the side including a switch or a diplexer.
However, the high-frequency module disclosed in Japanese Unexamined Patent Application Publication No. 2003-87076 has a problem in that, because the phase adjustment circuit is formed over an entire multilayer component, a module size is increased when an additional element, such as a switch element, is further mounted to the high-frequency module.
Moreover, in the above-described type of high-frequency module, a filter element, such as a SAW filter, must be used for each of the plurality of frequency bands, and the filter element must have a characteristic corresponding to each of the plurality of frequency bands. When a communication signal in a predetermined frequency band differing from the frequency bands capable of passing through the filter elements is sent and received through another circuit branched from a circuit including those filter elements, the following problem arises.
Because the filter elements have different phase characteristics from each other, respective phase adjustment circuits must be provided so as not to degrade the passage characteristics of the filter elements, taking into account respective reflection phases of all of the filter elements with respect to the predetermined frequency band. Thus, design of the phase adjustment circuits becomes difficult and the module size is increased. Another problem is that, when attempting to form a plurality of phase adjustment circuits in a small-sized multilayer module as described above, elements defining the phase adjustment circuits are positioned close to each other and isolation between the adjacent phase adjustment circuits is degraded.